A single-value metrics aggregation that keeps track and returns the minimum
value among numeric values extracted from the aggregated documents. These
values can be extracted either from specific numeric fields in the documents,
or be generated by a provided script.

The min and max aggregation operate on the double representation of
the data. As a consequence, the result may be approximate when running on longs
whose absolute value is greater than 2^53.

Let’s say that the prices of the documents in our index are in USD, but we
would like to compute the min in EURO (and for the sake of this example, let’s
say the conversion rate is 1.2). We can use a value script to apply the
conversion rate to every value before it is aggregated: